/Engine/Source/Runtime/RHI/Public/DynamicRHI.h
Function that is used to allocate / free space used for virtual texture mip levels. Make sure you also update the visible mip levels.
virtual void RHIVirtualTextureSetFirstMipInMemory ( class [FRHICommandListImmediate](API\Runtime\RHI\FRHICommandListImmediate) & RHICmdList, FRHITexture2D * Texture, uint32 FirstMip )